Reduction of chlorids.



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FRIEDRICH MEYER .AND HANS KERSTEIN, OF BERLIN, GERMANY.

REDUCTION OF CHLORIDS.

Specification of Letters Patent.

Patented Feb. 22, 1916.

Application led April 29, 1914. Serial No. 835,257.

To all whom it may concern.

Be it known that we, FRIEDRICH MEYER and HANS KERSTEIN, chemists,subjects of the German Emperor, both residing at Berlin, Germany, haveinvented certain new and useful Improvements Relating to the Reductionof Chlorids, of which the following is a specification.

The present binvention relates to the reduction of anhydrous chlorids,such as the chlorids of tin and titanium. The reduction of suchcompounds by means of gases, especially with hydrogen, is quite new asregards tin,.but not new inggeneral.

As a rule the compounds, if they are volatile, are exposed to hightemperatures in mixture with hydrogen, either by conducting them througha heated tube, or by causing the flame of an electric arc to burn in thegas-mixture. Very frequently these processes only lead to the next stageof reduction. For instance tetra-chlorid of tin yields dichlorid of tin,but never tin, tetrachlorid of titanium yieldstrichlorid of titanium,but the reduction never extends to the dichlorid or to metallictitanium. If the next stage of reduction is the metallic element, forinstance in the hitherto unknown reductionV of tin-dichlorid to tin,these processes give a bad yield.

We have discovered, that when applying the principleof reverse orcounter-currents in a special manner, surprising results may be obtainedin the reduction of such compounds. In the process hereafter describedthe reduction may be stopped at any desired stage of reduction, or vitmaybe carried out within a very simple" apparatus in such a manner, thatit leads from the starting material to the element, for instance fromtetrachlorid of tin to tin, from tetrachlorid of titanium to titanium,directly and continuously, while the whole quantity of the startingmaterial is utilized.

In dealing with a compound, such as the dichlorid of tin, which has onlyone nonvolatile reduction stage, it is suflicient to perform thereduction in a vertical tube, to introduce dichlorid and hydrogensimultaneously into the lower end of the tube, while taking care thatthe dichlorid, `which owing to equilibrium has not been reduced, flowsback by gravity into the reducing chamber, or in case the volatile bodysublimates, that the unreduced portion is caused to fall back bymechanical means. Still more important is the use of the principle ofreverse currents in the-case of chlorids, whose reductions take place inseveral stages, and where the usual reduction only leads to the nextstage of reduction. If in .this case the principle of reverse currents1s required to afford an advantage besides the usual better utilizationof the reducing agent, and if it is desired to insure, that thereduction proceeds further than usual, it is necessary, that the productor products of reduction move toward the relatively pure reducing agent,that is the reducing agent, which is free from the starting material.

The accompanying diagrammatic drawing serves to elucidate the process inthe case of the two chlorids of tin and of titanium, which have beenrepeatedly mentioned above.

Figurel indicates a vertical section of an apparatus suitable for thereduction of tinchlorids and Fig. 2 a vertical section of an apparatussuitable for the reduction of titanium chlorids.

If it is desired to reduce dichlorid of tin to tin, which corresponds toone stage of reduction, we employ the apparatus shown by F ig. 1, butomitting the tube b. Hydrogen is introduced through the tube c and atthe same time through the same tube dichlorid in a molten condition. Thezone A and B is then heated to 250o C. (the melting point of thedichlorid) and zone C to,a temperature between 600 and 1,000o C. Thedichlorid evaporates in this zone (also below its boiling point) and ispartially (viz: in accordance with the equilibrium corresponding to thetemperature), reduced to tin, which collects at the lower end of thetube and flows off through d. The hydrochloric acid and the excess ofhydrogen escape at the top of the tube. The dichlorid distilling offcondenses in the zones B and A and flows back to C, where finally it iscompletely reduced to tin.

If the process is carried out in the same manner, except that through ctetrachlorid of tin instead of dichlorid is introduced simultaneouslywith the hydrogen, the reduction takes place through only one stage, inspite of the reverse current principle, and dichlorid may be drawn o atd, but in that case the temperature of C must not be raised to 250 C.The reduction takes place soy that at the lower extremity of b and inzone B dichlorid `is formed, which condenses partly in zone B and partlyin zone A and descends to C. There it is reduced to tin, which ows offthrough d. Any dichlorid that may have been volatilized, returns throughzones B and A to C, while hydro chloric acid and excess of hydrogenescape from the apparatus at the top. The utility of the use of thereverse current principle in this form is apparent also from the secondexample, viz: its application to the reduction of titanic tetrachlorid.y

The reduction of titanium tetrachlorid to trichlorid succeedsquantitatively when the process given by St. Claire-Deville, or theso-called Deville tube, is employed. Its effect is based upon the quickchilling of the product of the reacting mixture previously highlyheated. The most favorable construction, especially for the presentcase, consists of two concentric tubes with the reaction compoundtherebetween, the one tube being maintained at a high temperature ofabout 900 to 1000 C., and the other tube being cooled down to a lowtemperature. Hydrogen, without being itself consumed, acts upon twomolecules of trichlorid under formation of one molecule of dichlorid andone molecule of tetrachlorid. The reaction that takes place is asfollows:

zTiCl3 H2 2TiC12 2HC1 gTiCl3 2HC1= 2T1Cli H2 y 4Tic1 zTiCl2 zTiCl,

Analogous is the action of hydrogen upon the dichlorid as follows:

with a yield of but 25%. If, however, the

reduction is performed by the above deyscribed process, the conversionmay be effected with a quantitative yield. The apparatus used for thispurpose is illustrated by FigyQ. Titanic tetrachlorid in the form ofvapor is introduced into the apparatus condition,

through tube and pure hydrogen throu h tube c. If it is desired toreduce only to i ichlorid, zone C is kept at a temperature below 700 C.,for reducing down to metallic titanium, a temperature of 800 to 900 C.is employed. Zone B must be kept at about 500 C., zone A is formed bywhat is known as va Deville tube. In this connection it should beobserved, that d indicates an internal heating device, for instance acarbon vrod rendered incandescenty by electrical means. g are the lowerleading-in wires for the heating body, Vwhich simultaneously serve asScrapers, for detaching from the cold Wall of the tube a the trichloridsettling on the same, so that it drops down to C by gravity. Current issupplied to the apparatus at ke and f through a revoluble cap mounted onthe tube a. The Scrapers g extend into the zone B having a temperatureof 500 C.

` In zone. A complete conversion of the tetrachlorid into trichloridtakes place. The ytrichlorid drops through B to C, where it is convertedinto titanium or titanium chlorid and tetrachlorid. vThe latter will,however, not escape,but will be re-converted at B into trichlorid. Apartial sublimation of dichlorid also takes place, which isheld back inzone B and caused to descend to C by the Scrapers. Finally the lowerpart of C will be filled with titanium, while only hydrochloric acid andexcess of hydrogen escape The present process seems to be specially Avaluable for utilizing the tetrachlorid of tin obtained inthe removal oftin from tinplate, and for obtaining certain metals, which otherwise aredifficult to obtain in a pure such as the titanium. The gaseous reducingagent may be, for instance a mixture of carbonio oxid and aqueous vaypor, instead of hydrogen, and the reduction may take place with the aidof pressure.

What we clai-m is 1. The process for the reduction by means of reducinggases of anhydrous chlorids yielding volatile intermediate productsduring the reduction, which consists in performing the reduction byusing the principle of reverse currents, in such a manner, that in casethere exist several stages of reduction, the products of the reductionare caused to move toward the pure reducing material, free from thestarting material, substantially as described. i

2. The process for reducing anhydrous volatile chlorids by means ofreducing gases, whichconsists in effecting the reduction by using theprinciple of reverse currents in such a manner, that the products of thereduction travel toward the pure reducing material free from startingmaterial, substantially as described.

3. The process of manufacturing tin, consisting in reducing dichlorid oftin in such manner that the product of reduction is caused to movetoward the reducing ma- 10 terial, the dichlorid, which, owing to thelequilibrium has not been reduced, fiowing back by gravity,substantially as described. In testimony whereof We have hereunto setour hands in presence of two subscribing Witnesses.

DR. FRIEDRICH MEYER. HANS KERSTEIN. Witnesses:

HENRY HASPER, VVOLDEMAR HAUPT.

